1. Field of the Invention
This invention relates to accessories for personal digital assistants (PDAs) and more particularly to a keyboard accessory for a PDA.
2. Description of the Related Art
Pen-based PDAs have grown in popularity for several reasons, chief amongst them being their small size and easy portability. Miniaturization of electronic components has made these devices increasingly powerful, versatile and affordable. Many users, however, find the two available stylus data-entry methods cumbersome and prone to errors. PDAs commonly rely on this stylus as a means for data entry. This involves tapping on an “on-screen software keyboard” or handwriting on a pressure-sensitive layer. The tapping method is typically slow, and the small screen area of PDAs increases the likelihood that a user will inadvertently make unintended selections. The handwriting recognition method affords the user greater flexibility and ease of use over the tapping method for composing messages and entering data, but handwriting recognition has its own set of limitations. The character recognition programs at the heart of these handwriting recognition methods often need to learn the handwriting of the user in order to be effective. Many users do not have the time or patience to bring their pen-based computer through this learning process. Even those users, that do train their pen-based computers to recognize their handwriting, find that mistakes are unavoidable since the art of handwriting recognition is far from perfect. Further, a pen-based computer trained to recognize one individual's handwriting will not function well if transferred to a second user, and may never function well if several users routinely use it.
There have been various attempts to provide suitable accessory keyboards to accommodate PDAs. For example, U.S. Pat. No. 6,108,200 issued to R. L. Fullerton, discloses a computer keyboard system that involves the user of a relatively large keyboard. A cover folds down over the keyboard; however, the cover and keyboard are substantially larger than the PDA, thus reducing the small size and easy portability advantages of using these PDAs. In one embodiment disclosed in the '200 patent, a smaller keypad is disclosed; however, that smaller keypad only includes the 10-key layout frequently used for inventory control. Furthermore, the '200 device requires the use of batteries and the PDA must be removed when not in use.
U.S. Pat. No. 6,147,858, issued to K. Takahashi, discloses another keyboard system. However, the keyboard disclosed is substantially smaller than the PDA and would not serve to protect it when in a stowed position. Furthermore, the Takahashi device has a limited number of keys and the PDA rests in the device. It is not locked in place.
U.S. Pat. No. 6,174,097, issued to S. R. Daniel, discloses a collapsible keyboard that is collapsible between a deployed configuration in which the keyboard is generally planar and a collapsed configuration, the keyboard being foldable about three substantially parallel axes between the deployed and collapsed configurations. The keyboard has four rigid subframes for supporting keys, each subframe being pivotally connected at a folding axis to an adjacent subframe. The keyboard preferably has support frames supporting keys thereon. The keys are slidable and are connected by flexible connectors that span the axes. The keyboard can be locked in either the collapsed or deployed configuration and can be combined with a remote communication unit. Due to it's collapsible nature the '097 device is not hand-held and cannot, for example, be supported on a lap.
Other full-size, or almost full-size, keyboards are conveniently available by several manufacturers' accessories, such as Palm, Outside the Box, GoType, Fellows, and others Generally, these accessory keyboards use the standard QWERTY configuration and need to rest on a flat surface in order for the user to use the keyboard with both hands. Often the accessory keyboard needs to be removed from the PDA when transported or not in use.
In attaching a portable keyboard assembly to a PDA one is presented with the problem of exclusively disabling the serial port of the PDA and exclusively enabling it as is desired. It is desired to provide the automatic enabling and disabling of the serial port without requiring user intervention required to accomplish this. To accomplish this, the designer of a keyboard modification system must be able to effectively patch into the operating system of the PDA. Additionally, if it is desired to utilize a keyboard modification system for use with a keyboard assembly having the capability of producing the characters that are produced by a conventional QWERTY keyboard (i.e. more than 150 characters), a significant design challenge is presented.